1. Technical Field
The invention concerns a process and a device for the registration of the state of wear of tools employed in gear manufacture.
In particular the invention concerns the registration of the state of wear of profiling tools which are employed for profiling machining tools, the machining tools being used for the continuous generation and profile grinding process and/or for gear honing. Such machining tools are in particular grinding worms and honing rings, and such profiling tools are in particular abrasive coated dressing discs and profiling gears.
2. Background of the Invention
On account of the high cost of tooling in gear manufacture, there is a need to supervise tool consumption, to make it controllable by calculation, and to make the different tools amenable to mutual comparison. This applies especially to the profile grinding and gear honing initially mentioned.
The state of wear of tools employed in gear manufacture cannot be checked by measurement. Moreover the development of wear on these tools and the factors influencing it are relatively complex. A registration of data is however made more difficult by the complexity of the machining process, and hence by the abundance of data. The difficulty in acquiring reliable data about the effective wear behaviour of these tools from use in industrial production is increased even more by the varying nature of use of the tools with frequent fresh set-ups on different machines by different setters and operators, and the changing conditions for different diameters of the tools to be profiled. Yet the knowledge of the state of wear and the effective piece potential of these tools is essential both for an efficient tool management and for optimizing the conditions of use, as well as for the technical further development of the tools by the tool manufacturer. Furthermore, the profiling tools in particular often have a very long life and are employed on a wide variety of machines, which in turn makes the registration, the supervision and the exchange of data still more difficult.
Tool consumption has hitherto been measured simply by the number of workpieces produced. This characteristic quantity certainly offers the advantage that the proportion of tooling costs per workpiece can be easily calculated, but has the disadvantage that in the event of the calculated number of workpieces produced not being attained the causes of the deviation are not discernible. In particular it offers no information as to whether or how severely grinding or honing tools have been xe2x80x9cover-profiledxe2x80x9d. xe2x80x9cOver-profilingxe2x80x9d means, for example, avoidable initial profiling or intermediate profiling operations which contribute to profiling tool wear without workpieces having been produced, or profiling operations under unsuitable profiling conditions that increase tool wear, which likewise results in a reduction of the piece potential. Piece potential is understood as the number of workpieces produced during the entire period of use of the machining tool.
For tools used in gear manufacture, a detailed determination of wear behaviour is thus only possible when on the one hand the tool consumption can be expressed by calculation, and on the other hand the actual state of wear of the tool can be assessed.
Various methods are known by which tool data can be registered, stored, and applied for optimizing the use, for the tool management and for further development of the tools.
On machining centres especially, for example, the tools or their tool holders are often provided with an electronic data carrier, from which the stored data can be read by a machine control system via a write/read unit, and on which the machine control system can write other tool or process data. For machine tools such as are encountered in gear manufacture, however, the use of suitable data carriers integrated in the tool or tool holder is impossible. The storage capacity of integrated data carriers is insufficient for the abundance of data involved.
EP-A-1,043,118 presents further a process for registering information on the use of a tool, by which the use data of the tool is processed in a data bank of the machine control system and transmitted to tool management or to a tool manufacturer either via a data network or by a data carrier copy. This solution presumes that an appropriate data structure, a suitable storage organization as well as suitable data transfer channels are available, in order to assure the registration and transmission of the entire relevant use data of a tool, even in the case of extremely long tool life. In the case of gear manufacturing machines, especially for the profiling tools used in gear manufacture, this is very complicated and extravagant, and is hence not available here.
Furthermore no process is as yet known, by which the piece potential of profiling tools on machines operating by the continuous profile grinding method and/or by gear honing can be determined by calculation, and the actual state of wear assessed during use.
It is an object of the present invention to provide a process and a device for determining the state of wear of tools employed in gear manufacture, which obviate the above-mentioned disadvantages.
This object is achieved by a process and a device having the features of patent claims 1 and 13 respectively.
It is a further object of the invention to create a device for determining the state of wear, which allows an unambiguous allocation of a data carrier to the tool.
This object is achieved with a device having the features of claim 14.
The invention is rooted, on the one hand, in the finding that under invariable wear intensity the cutting distance travelled per abrasive coated surface until the tool is spent is largely of at least approximately constant magnitude, and moreover independent of the relevant tooth geometry of the tool. In the following this value is termed the life path constant. In the case of gear-shaped tools, a further finding applied is that the wear that governs the failure of the tool is concentrated at the tooth tip zone, even if both tooth tip and tooth flanks are subjected to the machining stress. It is further considered that the wear development of the tool progresses approximately linear relative to the cutting distance of the tooth tip, which is proportional to the momentary diameter of the grinding worm.
Basing on these findings, in the process according to the invention for registering the state of wear on a tool, the cutting distance per tooth tip is determined and, after weighting with a wear intensity factor, compared with the life path constant.
If the registered weighted cutting distance equals the life path constant, a maximum acceptable state of wear has theoretically been reached. If it is not yet equal to the life path constant, it is possible to derive the number of workpieces that can still be machined with this tool or with a machining tool prepared with this tool. This quantity is termed the residual piece potential. It is furthermore possible to derive evidence concerning the basic wear behaviour and an overall assessment of the tool, which permit conclusions as to useful and/or necessary improvement measures to the machining process, and also the residual piece potentials of the tool under unaltered or improved operating conditions.
The process and the device according to the invention are especially suitable for registering the state of wear of profiling tools which are employed for profiling gear grinding or honing tools. In particular they are suitable for profiling tools in the form of a gear, which are employed for profiling grinding worms used in continuous profile grinding. In this case, by way of the determined state of wear of the profiling tool, the total piece potential and residual piece potential of the grinding worm producing the workpieces can also be derived.